U.S. Pat. Nos. 4,343,536 to Bartlett et al and 4,342,536, to Akeel et al disclose apparatus for opening and closing doors on a vehicle body during the painting of the vehicle body by a robot. The apparatus includes primary and auxiliary arms mounted on a carriage. The apparatus is taught to follow the vehicle body as it moves through a painting station. During this tracking operation, the secondary arm of the apparatus is extended to engage a fixture mounted to a door of the vehicle body. The door is opened by driving the fixture through an arc predetermined by the relationship between the fixture and the door hinge axis. The apparatus includes hydraulic motors, servo valves, resolvers, gear boxes, a pneumatic cylinder and a control valve. Considerable electronics are involved in the control portion of the apparatus to provide continuous feedback and command signals. The electronics also contains therewithin the various paths corresponding to various body style door configurations. Numerous electrical, hydraulic and pneumatic lines extend to the moving parts of the apparatus.